How do I programmatically add a view right under the navigation bar?

问题

I'm trying to add a view to a UINavigationController with its top aligned with the navigation bar's bottom.

I tried using constraints by adding the following to my UINavigationController subclass:

override func viewDidAppear(_ animated: Bool) {
           self.label = UILabel()
    self.label?.translatesAutoresizingMaskIntoConstraints = false
    self.label?.backgroundColor = UIColor.red
    self.label?.text = "label text"
    self.view.addSubview(self.label!)
    let horConstraint = NSLayoutConstraint(item: label!, attribute: .top, relatedBy: .equal,
                                           toItem: topLayoutGuide, attribute: .bottom,
                                           multiplier: 1.0, constant: 0.0)
    let widthConstr = NSLayoutConstraint(item: label!, attribute: .width, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1, constant: 100)

    let heightConstr = NSLayoutConstraint(item: label!, attribute: .height, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1, constant: 100)
    view.addConstraints([horConstraint, widthConstr, heightConstr])
}

With this being the result:

And I tried by setting the frame of my subview:

override func viewDidAppear(_ animated: Bool) {

    self.label = UILabel(frame: CGRect(x: 0, y: navigationBar.frame.height, width: 300, height: 100))
    self.label?.translatesAutoresizingMaskIntoConstraints = false
    self.label?.backgroundColor = UIColor.red
    self.label?.text = "label text"
    self.view.addSubview(self.label!)

}

And this came out:

In both cases my label covers part of the navigation bar. How to I fix this?

回答1:

Height of status bar is 20.You should consider status bar also while assigning y of your label. Your viewDidAppear should be

override func viewDidAppear(_ animated: Bool) {

    self.label = UILabel(frame: CGRect(x: 0, y: navigationBar.frame.height+20, width: navigationBar.frame.width, height: 100))
    self.label?.translatesAutoresizingMaskIntoConstraints = false
    self.label?.backgroundColor = UIColor.red
    self.label?.text = "label text"
    self.view.addSubview(self.label!)
 }

Hope it helps. Happy Coding!!

回答2:

Swift 4.

Try this code with NSLayoutConstraint. newView will appear right under NavigationBar

        self.edgesForExtendedLayout = []//Optional our as per your view ladder

        let newView = UIView()
        newView.backgroundColor = .red
        self.view.addSubview(newView)
        newView.translatesAutoresizingMaskIntoConstraints = false
        if #available(iOS 11.0, *) {
            let guide = self.view.safeAreaLayoutGuide
            newView.trailingAnchor.constraint(equalTo: guide.trailingAnchor).isActive = true
            newView.leadingAnchor.constraint(equalTo: guide.leadingAnchor).isActive = true
            newView.topAnchor.constraint(equalTo: guide.topAnchor).isActive = true
            newView.heightAnchor.constraint(equalToConstant: 50).isActive = true
        } else {
            NSLayoutConstraint(item: newView,
                               attribute: .top,
                               relatedBy: .equal,
                               toItem: view, attribute: .top,
                               multiplier: 1.0, constant: 0).isActive = true
            NSLayoutConstraint(item: newView,
                               attribute: .leading,
                               relatedBy: .equal, toItem: view,
                               attribute: .leading,
                               multiplier: 1.0,
                               constant: 0).isActive = true
            NSLayoutConstraint(item: newView, attribute: .trailing,
                               relatedBy: .equal,
                               toItem: view,
                               attribute: .trailing,
                               multiplier: 1.0,
                               constant: 0).isActive = true

                newView.heightAnchor.constraint(equalToConstant: 50).isActive = true
        }

回答3:

You're not calculating the height of the status bar with the navigation bar. In total they are 64, 44 nav bar and 20 for the status bar

回答4:

Frame of navigationBar is (0 20; 375 44), you can set label y position to 64.

回答5:

Replace this

self.label = UILabel(frame: CGRect(x: 0, y: navigationBar.frame.height, width: 300, height: 100))

with

self.label = UILabel(frame: CGRect(x: 0, y: 64, width: 300, height: 100))

naviagtion bar & status bar together has a height of 64. Make it the y position

回答6:

override func viewDidAppear(_ animated: Bool) {
let label = UILabel(frame: CGRect(x: 0, y: (navigationController?.navigationBar.frame.height)! + 20, width: UIScreen.main.bounds.width, height: 40))
label.translatesAutoresizingMaskIntoConstraints = true
label.text = "Hello"
label.backgroundColor = UIColor.red
self.view.addSubview(label)

}

来源：https://stackoverflow.com/questions/44966786/how-do-i-programmatically-add-a-view-right-under-the-navigation-bar

标签

ios

swift

uiview